Liquid crystal display device and method of fabricating the same

ABSTRACT

A liquid crystal display device includes a substrate, a black matrix layer on the substrate and having a first plurality of openings, a color filter layer on the black matrix layer and having a second plurality of openings, and a plurality of column spacers each contacting the substrate through the first plurality and second plurality of openings.

The present invention claims the benefit of Korean Patent ApplicationNo. 88471/2002 filed in Korea on Dec. 31, 2002, which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color filter substrate structure of aliquid crystal display device, and more particularly, to a method offabricating a color filter substrate having a spacer directly contactinga substrate.

2. Description of the Related Art

Presently, liquid crystal display (LCD) devices are commonly used invarious fields from image display devices, such as computer monitors, TVreceivers, and portable telephones, to information display panels usedfor automobiles and airplanes, for example.

FIG. 1 is a perspective view of an upper substrate and a lower substrateof an LCD device according to the related art. In FIG. 1, an LCD deviceincludes a transparent substrate 21, a color filter layer 8 including ablack matrix 6 and a sub-color filter layer 7 of red, green, and blue onthe transparent substrate 21, a color filter substrate 1 having atransparent common electrode 18 on the color filter layer 8, a TFT arraysubstrate 2 including a plurality of switching devices T arranged on thesubstrate 3 in a matrix configuration, and a pixel electrode 5corresponding to the respective switching devices T. In addition, aliquid crystal material 10 is injected between the color filtersubstrate 1 and the TFT array substrate 2.

A plurality of gate lines 11 arranged in rows and a plurality of datalines 12 arranged in columns are on formed on the TFT array substrate 2,such that the gate and data lines intersect and cross each other. Inaddition, a thin film transistor T corresponding to the switching deviceis formed at the intersection points between the gate lines and the datalines in a matrix configuration.

A pixel region 4 is formed on the TFT array substrate 2 corresponding tothe gate lines 11 and the data lines 12, and the pixel electrodeS isformed on the pixel region 4. The pixel electrode 5 is formed of atransparent electrode material having excellent light transmittance,such as Indium Tin Oxide (ITO).

FIG. 2 is a flow chart for a fabrication process of an LCD deviceaccording to the related art. In FIG. 2, the fabrication processincludes steps of: preparing a lower (TFT) substrate; forming analignment layer on the lower substrate; rubbing the alignment layer foralignment of liquid crystal material (not shown); forming a sealpattern; scattering spacers (not shown); bonding an upper substrate andthe lower substrate together; cutting the bonded substrates into aplurality of unit cells; and injecting the liquid crystal material intothe unit cell.

During the preparation of the lower substrate, a plurality of the gatelines horizontally arranged and a plurality of the data lines verticallyarranged by crossing the gate lines are formed on the lower substrate.Then, a plurality of the thin film transistors are formed in a matrixconfiguration at the intersection points of the gate lines and the datalines. Next, the pixel electrode corresponding to the switching device Tis formed on the TFT array substrate.

During the formation of the alignment layer, a thin film of polymermaterial is uniformly coated on the lower substrate. It is essentialthat the alignment layer is uniformly formed so that the subsequentprocess of rubbing the alignment layer may be uniformly performed andalignment of the liquid crystal material may be uniform.

During the process of rubbing the alignment layer, a cloth is used torub the alignment layer along a constant direction to uniformly alignthe liquid crystal material. The rubbing process is important to set theinitial alignment direction of the liquid crystal material. When therubbing process is properly performed, normal driving of the liquidcrystal material is possible to provide uniform driving characteristicsof the LCD device. Generally, the alignment layer is formed ofpolyimide-based organic materials.

The seal pattern forms a gap between the upper substrate and the lowersubstrate for the liquid crystal material injection, and prevents theinjected liquid crystal material from leaking out from the bondedsubstrates. Accordingly, during the formation process of the sealpattern, a constant pattern is formed along a periphery of an activeregion of the lower substrate using a thermosetting resin during ascreen printing method.

During the process of scattering the spacers, spacers of a predeterminedsize are used in order to maintain a constant cell gap between the upperand lower substrates. Accordingly, the spacers have to be scattereduniformly on the TFT array substrate. Scattering methods of the spacersinclude a wet scattering method for scattering the spacers within analcohol carrier solution, and a dry scattering method for scatteringonly the spacers without using a carrier solution. In addition, the dryscattering method includes an electrostatic scattering method usingstatic electricity, and a non-electrostatic scattering method using gaspressure. The non-electrostatic scattering method is commonly used inthe liquid crystal cell structure having a low static electricityresistance.

During the bonding process, the upper and lower substrates are bondedtogether along the seal pattern. The bonding process is determined by apredetermined margin between the upper and lower substrates, which maybe several microns. If the bonded substrates exceed the predeterminedmargin, light may leak from the liquid crystal display device, therebyreducing the picture quality of driving the liquid crystal displaydevice.

Next, the bonded substrates are divided into a plurality of unit cellsby cutting the upper and/or lower substrates. In previous processes forcutting the liquid crystal cells, the liquid crystal material wassimultaneously injected into several unit cells and the cells were cutas a unit cell. However, as the area of the LCD devices increased, theliquid crystal cells were first cut into the unit cells and theninjected with the liquid crystal material.

Finally, the liquid crystal material is injected into the cut unitliquid crystal cells. The unit liquid crystal cell has a cell gap ofseveral microns and an area of several hundreds of square centimeters.Accordingly, a vacuum injection method for -injecting the liquid crystalmaterial into the unit liquid crystal cells using a pressure differencebetween interior and exterior regions of the liquid crystal cells iscommonly used.

FIGS. 3A to 3F are cross sectional views of a fabrication process of anupper substrate of an LCD device according to the related art. In FIG.3A, a black matrix 32 is formed on a transparent glass substrate 31 at aregion of an upper substrate that corresponds to gate and data lines andswitching devices of the lower substrate. Generally, the black matrix 32is formed between sub-color filter of red, green, and blue, and blockslight that passes through a reverse tilt domain formed at a peripheralportion of a pixel electrode of the lower substrate. A material forforming the black matrix 32 includes a metal thin film, such as Cr,having an optical density more than 3.5, or an organic material. Inaddition, a double layer, such as Cr/CrOx, may be used for lowreflection. Accordingly, a proper material of the black matrix may beselected for a desired purpose.

In FIG. 3B, a color filter is formed using a pigment scattering method.However, several different methods may be used, such as dyeing,depositing, and printing. First, a red color resin is deposited on thesubstrate 31 upon which the black matrix 32 has been previously formed.Then, the red color resin is selectively exposed to light, therebyforming a red sub color filter 33 a at a desired region.

Next, a green color resin is deposited on the substrate upon which thered sub-color filter has been previously formed, and selectively exposedto light, thereby patterning the green sub-color filter 33 b at adesired region. Likewise, a blue sub-color filter 33 c is formed byrepeating the same process.

In FIG. 3C, a process for forming a overcoat layer 34 includes forming atransparent resin having an insulating characteristic on the substrate31 upon which the sub-color filters 33 a, 33 b, and 33 c have beenpreviously formed, thereby forming an overcoat layer 34. The overcoatlayer 34 is not necessarily formed and may be omitted. When a Cr-basedmetal is used as the black matrix 32, the overcoat layer 34 is notneeded since a thickness of the black matrix 32 is as thin as a fewthousands of angstroms. In addition, when a resin-based black matrix 32is used, a thickness may be 1 to 1.5 μm, thereby requiring the overcoatlayer 34.

In FIG. 3D, a common electrode 35 is formed on the color filtersubstrate upon which the overcoat layer 34 has been previously formed.The common electrode is a transparent electrode and is commonly formedof indium tin oxide (ITO). A common voltage is supplied to the commonelectrode, so that an electric field is formed in combination with apixel voltage applied to the pixel electrode on the array substrate,thereby driving the liquid crystal material.

In FIG. 3E, spacers 36 are formed in which a transparent organic film isformed on the substrate 31 upon which the common electrode 35 has beenpreviously formed, and the spacers 36 are patterned with a specificshape by photolithographic and an etching processes. Both shape andheight of the spacers 36 are determined by the photolithographic processthat includes a chemical reaction by irradiation of light and crosslinking. Accordingly, the construction of the spacers 36 is changed intoa net structure and the spacers 36 are resistant to etching. Thus, thespacers 36 may be formed having a more minute pattern, therebyincreasing the mechanical strength of the spacers 36. Increasing themechanical strength of the spacers 36 results in increasing mechanicaldeformation of the spacers. For example, in in-plane switching (IPS)mode LCD devices, an electric field is formed on the array substrate 31and the metal-based black matrix may influence the electric field whenthe liquid crystal material is driven. Accordingly, carbon-based resinsare used as the material of the black matrix 32. However, thecarbon-based black matrix resins have a mechanical strength lower thanthat of the acryl-based color resin and the overcoat layer 34 so thatthe black matrix resin 32 is mechanically deformed by external impact tothe spacers 36. In addition, the spacers 36 can be formed on theovercoat layer 34 prior to formation of the common electrode 35.However, the same problems regarding mechanic deformation may begenerated.

In FIG. 3F, a process for forming the alignment layer 37 includesforming an organic insulating film, such as polyimide, on the colorfilter substrate upon which the spacers have been previously formed.Then, a rubbing process is performed for forming a predetermined grooveon the alignment layer 37 in order to provide an alignment of the liquidcrystal material, thereby completing the upper substrate of the LCDdevice.

It is possible that the spacers 36 can be formed after forming thealignment layer 37. However, the alignment layer 37 is chemicallydamaged during the etching process. Thus, the alignment layer 37 iscommonly formed after formation of the spacers 36.

However, during fabrication of the upper substrate of the LCD device andfabrication of the spacers 36, the spacers 36 are formed at a regioncorresponding to the black matrix 32. When external pressure is appliedto the spacers 36, the carbon resin-based black matrix 32 correspondingto bottom portions of the spacers 36 are mechanically deformed such thatthe spacers 36 are deformed along a direction towards the black matrix32. This is a significant problem in IPS-mode LCD devices that use thecarbon resin-based black matrix. If the spacers are deformed, the cellgap is not uniformly maintained. Accordingly, differences in displayedimage brightness are generated, thereby creating smear on the imagescreen. This phenomenon is also generated where the spacers 36 areformed at a color filter region of the upper substrate corresponding tothe pixel region of the TFT array substrate of the LCD device.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device and method of fabricating a liquid crystal display devicethat substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a liquid crystaldisplay device having an improved a cell gap structure.

Another object of the present invention is to provide a liquid crystaldisplay device having an improved spacer structure to prevent blackmatrix destruction.

Another object of the present invention is to provide a method offabricating a liquid crystal display device having an improved a cellgap structure.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, aliquid crystal display device includes a substrate, a black matrix layeron the substrate and having a first plurality of openings, a colorfilter layer on the black matrix layer and having a second plurality ofopenings, and a plurality of column spacers each contacting thesubstrate through the first plurality and second plurality of openings.

In another aspect, a liquid crystal display device includes a substrate,a black matrix layer on the substrate and having a first plurality ofopenings, a color filter layer on the black matrix layer, a plurality ofcolumn spacers on the color filter layer, and an alignment layer on thesubstrate, wherein the plurality of column spacers are aligned with thefirst plurality of openings.

In another aspect, a method for fabricating a liquid crystal displaydevice includes forming a black matrix layer on a substrate, forming acolor filter layer on the black matrix layer, forming a first pluralityof openings through the color filter layer and black matrix layer toexpose a surface portion of the substrate, and forming a plurality ofcolumn spacers within the first plurality of openings.

In another aspect, a method for fabricating a liquid crystal displaydevice includes forming a black matrix layer on a substrate, forming afirst plurality of openings in the black matrix layer to expose surfaceportions of the substrate, forming a color filter layer on the blackmatrix layer, and forming a plurality of column spacers on the colorfilter layer.

In another aspect, a liquid crystal display device includes a substrate,a black matrix layer on the substrate and having a first plurality ofopenings, a first color filter layer on the black matrix layer, a secondcolor filter layer on the black matrix layer and within the firstplurality of openings, an overcoat layer on the first and second colorfilter layers, a common electrode layer on the overcoat layer, and aplurality of column spacers on the common electrode layer.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a perspective view of an upper substrate and a lower substrateof an LCD device according to the related art;

FIG. 2 is a flow chart for a fabrication process of an LCD deviceaccording to the related art;

FIGS. 3A to 3F are cross sectional views of a fabrication process of anupper substrate of an LCD device according to the related art;

FIGS. 4A to 4G are cross sectional views of an exemplary fabricationprocess of an upper substrate of an LCD device according to the presentinvention; and

FIGS. 5A to 5C are cross sectional views of another exemplaryfabrication process of an upper substrate of an LCD device according tothe present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIGS. 4A to 4G are cross sectional views of an exemplary fabricationprocess of an upper substrate of an LCD device according to the presentinvention. In FIG. 4A, a substrate 41 of an LCD device may be preparedto include, but not limited to, a plurality of gate and data lines,switching devices, and pixel electrodes. Then, a black matrix 42 may beformed on the substrate 41 for covering the gate lines, data lines, andswitching devices. Alternatively, the gate lines, data lines, andswitching devices may be formed on a lower substrate of the LCD device.The black matrix 42 may be formed between sub-color filters of red,green, and blue, thereby blocking light that may pass through a reversetilt domain formed along a peripheral portion of a pixel electrode ofthe lower substrate.

The black matrix 42 may include a metal thin film, such as Cr, or anorganic carbon resin may be used. The black matrix 42 made of a Crmaterial may be used in LCD devices of a) twisted nematic (TN) mode,wherein a common electrode may be located on the upper substrate and apixel electrode may be formed on the lower substrate. In addition, in anIPS mode the common electrode and the pixel electrode may be formed onthe same substrate, i.e., the lower substrate. Accordingly, sincemetallic materials used to make the black matrix 42 may influence anelectric field generated by the common and pixel electrodes of the lowersubstrate a carbon resin black matrix material may be used. The presentinvention may improve the brightness of the LCD device using the carbonresin as a material of the black matrix 42. In addition, the carbonresin may also be used as a material of the black matrix 42 in the TNmode LCD device.

In FIG. 4B, a color filter having color resins of red, green, and bluemay be formed on the substrate 41 and portions of the black matrix 42using a pigment scattering method, for example. The color resin includesphotosensitive color resins, such as monomers, and binder.Alternatively, several different methods may be used, such as dyeing,depositing, and printing.

First, the red color resin may be coated on an entire surface of thesubstrate 41 upon which the black matrix 42 may have previously beenformed. Then, the red color resin may be selectively exposed to light,thereby forming a red sub-color filter 43 a at desired regions of thesubstrate 41 and the portions of the black matrix 42.

Next, the green color resin may be coated on the substrate 41 upon whichthe red sub-color filter 43 a may have previously been formed. Then, thegreen color resin may be selectively exposed to light, thereby formingthe green sub-color filter 43 b at desired regions of the substrate 41and the portions of the black matrix 42.

Similarly, a blue sub-color filter 43 c may be formed by repeating theabove process. A fabrication order of the red, green, and blue sub-colorfilters 43 a, 43 b, and 43 c may be rearranged.

In FIG. 4C, an overcoat layer 44 made of a transparent acryl resin maybe formed to compensate for any stepped regions between the black matrix42 and the red, green, and blue sub-color filters 43 a, 43 b, and 43 c.

In FIG. 4D, a common electrode 45 may be formed on the overcoat layer44. The common electrode 45, together with a pixel electrode formed onanother substrate, may be used for supplying an electric field to theliquid crystal material, which will be subsequently formed. However, inthe IPS mode LCD device, the common electrode may not necessarily berequired.

In FIG. 4E, portions of the common electrode 45, the overcoat layer 44,the sub-color filters 43 a, 43 b, and 43 c (collectively referred to asa color filter layer 43), and the black matrix 42 on the substrate 41may be partially removed by etching to expose a portion of the substrate41 through opening 46. Alternatively, the common electrode 45, theovercoat layer 44, the color filter layer 43, and the black matrix 42may be selectively formed to provide the opening 46 such that etchingmay not be necessary.

Since a portion of the black matrix 42 formed on the substrate 41 may beremoved, light may leak from the lower substrate through the opening 46.Accordingly, a spacer may be formed within the opening 46 that is formedof a material that can block the leaked light, such as a colored resinmaterial.

In FIG. 4F, the black matrix 42 (in FIG. 4E) may be formed within aregion of the blue sub-color resin 43 c since the blue sub-color resin43 c may have the highest intensity among the red, green, and bluesub-color resins 43 a, 43 b, and 43 c. In addition, a size of theopening 46 may be approximately 10 μm in diameter.

In FIG. 4G, the spacer 47 may be formed using a photosensitive resin andmay be formed using photolithographic and etching processes so that thespacer 47 may be precisely aligned within the opening 46 (in FIG. 4F).Specifically, the column spacer 47 may include a matrix resin dissolvedand swelled by alkaline aqueous solution, acryl monomer having ethyleneunsaturated bonding number more than 2, or photo-polymerizationinitiator may be used. In addition, a width between sidewall portions ofthe opening 46 may be at least similar to a width of a bottom portion ofthe column spacer 47.

Although not specifically shown, a single spacer may be distributedamong three adjacent pixel regions, or more. In addition, the spacer maybe formed to maintain a cell gap of about 3 to 7 μm between the upperand lower substrates of the LCD device. Moreover, since the spacers maybe formed to directly contact the glass substrate 41, the spacers mayhave a relatively larger size as compared to spacers according to therelated art.

FIGS. 5A to 5C are cross sectional views of another exemplaryfabrication process of an upper substrate of an LCD device according tothe present invention. In FIG. 5A, a black matrix 52 may be formed on asubstrate 51.

In FIG. 5B, portions of the black matrix 52 located at a point wherespacers may be subsequently formed on the substrate 51 may be removed byphotolithographic and etching processes, thereby exposing surfaceportions of the substrate 51. In addition, one opening 53 may bedistributed among at least three adjacent pixel electrodes, or more. Theopening 53 may be larger than the subsequently formed column spacersince the column spacer will formed within the opening 53. When theopening 53 is smaller than the column spacer, the black matrix 52 andthe column spacer may overlap after arranging the column spacer withinthe opening 53. Thus, when an external pressure is applied, the blackmatrix 52 may be mechanically deformed, as in the related art. Since asize of the column spacer is approximately 10 μm in diameter, theopening 53 on the black matrix 52 should be larger than the 10 μm, ormay be the same.

After forming the opening 53 in the black matrix 52, red, green, andblue sub-color resins (collectively called the color filter resin) maybe applied by a pigment scattering method, for example, similar to theprocess shown in FIG. 4B. Then, as shown in FIG. 5C, an overcoat layer55 and a common electrode 56 may be sequentially formed similar to theprocesses shown in FIGS. 4C and 4D.

FIG. 5C is a cross sectional view of the upper substrate of the LCDdevice when a dotted line 5L is a cutting line in FIG. 5B. Since thecolor filter resin may be arranged as a stripe on the substrate wherethe black matrix 52 is arranged, the color filter resin 54 may belocated within the opening 53 and on the black matrix 52. In addition,column spacers 57 may be formed on the common electrode 56 aligned tothe opening 53.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice and method of fabricating the same of the present invention withdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-8. (canceled)
 9. A liquid crystal display device, comprising: asubstrate; a black matrix layer on the substrate and having a firstplurality of openings; a color filter layer on the black matrix layer; aplurality of column spacers on the color filter layer; and an alignmentlayer on the substrate, wherein the plurality of column spacers arealigned with the first plurality of openings.
 10. The device accordingto claim 9, wherein a width between sidewall portions of each of thefirst plurality of openings is at least similar to a width of bottomportions of each of the plurality of column spacers.
 11. The deviceaccording to claim 9, further comprising an overcoat layer on the colorfilter layer.
 12. The device according to claim 9, further comprising acommon electrode on the color filter layer. 13-18. (canceled)
 19. Amethod for fabricating a liquid crystal display device, comprising:forming a black matrix layer on a substrate; forming a first pluralityof openings in the black matrix layer to expose surface portions of thesubstrate; forming a color filter layer on the black matrix layer; andforming a plurality of column spacers on the color filter layer.
 20. Themethod according to claim 19, wherein the plurality of column spacersare integrally formed with the first plurality of openings.
 21. Themethod according to claim 20, wherein a width between sidewall portionsof each of the first plurality of openings is at least similar to awidth of bottom portions of each of the plurality of column spacers. 22.A liquid crystal display device, comprising: a substrate; a black matrixlayer on the substrate and having a first plurality of openings; a firstcolor filter layer on the black matrix layer; a second color filterlayer on the black matrix layer and within the first plurality ofopenings; an overcoat layer on the first and second color filter layers;a common electrode layer on the overcoat layer; and a plurality ofcolumn spacers on the common electrode layer.
 23. The device accordingto claim 22, wherein the plurality of column spacers are aligned withthe first plurality of openings.
 24. The device according to claim 22,wherein a width between sidewall portions of each of the first pluralityof openings is at least similar to a width of bottom portions of each ofthe plurality of column spacers.
 25. The device according to claim 24,wherein a diameter of the plurality of column spacers is approximately10 μm.
 26. The device according to claim 22, wherein each of the firstplurality of openings are distributed among at least three adjacentpixel electrodes.
 27. The device according to claim 26, wherein each ofthe first plurality of openings are distributed among more than threeadjacent pixel electrodes.